Vision systems that perform measurement, inspection, alignment of objects and/or decoding of symbology (e.g. bar codes) are used in a wide range of applications and industries. These systems are based around the use of an image sensor, which acquires images (typically grayscale or color, and in one, two or three dimensions) of the subject or object, and processes these acquired images using an on-board or remote, interconnected vision system processor. The processor generally includes both processing hardware and non-transitory computer-readable program instructions that perform one or more vision system processes to generate a desired output based upon the image's processed information. This image information is typically provided within an array of image pixels each having various colors and/or intensities. In the example of a symbology (barcode) reader, the user or automated process acquires an image of an object that is believed to contain one or more barcodes. The image is processed to identify barcode features, which are then decoded by a decoding process and/or processor obtain the inherent alphanumeric data represented by the code. In other types of vision systems, various vision system tools (e.g. edge detectors, calipers, blob analysis) are employed by the system processor to detect edges and other features that allow for recognition of object features, and the determination of desired information based upon these features—for example whether the object is defective or whether it is properly aligned.
It is increasingly desirable to provide vision systems and associated vision system components that can be used for a variety of purposes and a range of environments. Likewise, vision systems that can take advantage of improved technologies, such as more-efficient illuminators are desirable. In any vision system, a major component is the vision system camera assembly. The camera assembly includes a lens (optics) and an imager (or “sensor”) that provides the array of image pixel information. The vision system processor receives the pixel data from the imager/sensor and processes it to derive useful vision system information about the imaged scene and/or object. The vision system processor and related components (e.g. data memory, decoders, etc.) can be provided within the camera assembly's physical housing or enclosure, or some or all of these vision processing components can be mounted remotely (e.g. within a PC, or other remote, self-contained processing system), and linked by a wired or wireless interconnect.
Another significant component of many vision system cameras is the illumination assembly. To adequately acquire an image of an object's (or scene's) surface, it is desirable to illuminate it with illumination that exhibits the appropriate intensity, spread, wavelength and timing for a particular acquisition task. Depending upon the features being imaged and the relative angle of the camera axis to the features, the type and characteristics of illumination employed can vary widely. For example, some features (e.g. peened features) can be best imaged using low-angle illumination, while other features (e.g. printed, high-contrast features) are typically best imaged using direct, high-angle illumination. Likewise, the wavelength of illumination can vary depending on the nature of the features—that is, some features are best illuminated in the visible range, while others may be enhanced using infrared (IR) or ultraviolet (UV) light. Likewise, for some applications it is desirable to employ polarized light and/or to filter the light entering the camera with a polarizer or other appropriate optical filter. Many camera systems include a ring illumination arrangement consisting of one or more rows of that encircle the camera lens. These illuminators can be external and remote from the camera housing, but are also often “internal”, being fixed in place on the front of the camera. A common form of ring illuminator, which surrounds the camera lens, is constructed on a circuit board that contains a predetermined number of lighting elements in one or more circles around the lens axis. The lighting elements on a typical illuminator are LEDs, but other types of light sources (e.g. xenon strobes, laser diodes, etc) can also be employed, either as an alternative to LEDs or in addition to LEDs.
In an external illuminator, a dedicated light arrangement is typically used to provide desired illumination to the scene from a desired vantage point that can be remote from the camera and its lens axis. It is typically interconnected with the camera assembly or other device by a cable that provides trigger signals from the camera and can provide other data to and from the camera. The external illuminator is typically pre-configured with an appropriate light source, controller, and interface circuit that is adapted to connect to most camera assemblies. The external lighting arrangement is typically user-installable and configurable.
With conventional internal lighting systems, most camera manufacturers prevent the user from installing or changing-out the lighting system that is integrated in the camera. One reason that the internal illumination assembly is not adapted for exchangeability is that there exists a risk of installation and/or configuration errors by the end user. This is because the camera may be set to acquire images based upon a certain set of illumination parameters, that when changed, may not be accommodated by the camera's vision processor (or “core”) and lighting controller. These illumination parameters can include (but are not limited to) operating voltage and current, startup timing, maximum time on, maximum temperature, maximum power and the light intensity for a given level of output current. Failure to properly accommodate these parameters within the camera can result in poor image acquisition or even damage to the equipment.
As noted above, the ability to provide a more-versatile and upgradable vision system is desirable. Part of the desired versatility and upgradability is the ability to provide an illuminator to the camera that is particularly suited to the vision task and straightforward to set up without the risk of improperly setting parameters. Moreover, the ability to change out that illuminator at a subsequent time (e.g. in the field) is further desirable). This exchangeability is particularly desirable with illuminators that are controlled internally, but also with external illuminators that may require some control by the camera assembly.